Research Status and Development Prospects of Radio Frequency Identification (RFID) Technology

Currently, RFID has become a research hotspot in the IT industry and is regarded as the next "gold mine" of the IT industry. Major software and hardware manufacturers, including IBM, Motorola, Philips, TI, Microsoft, Oracle, Sun, BEA, SAP, etc., have shown great interest in RFID technology and its applications, and have successively invested a large amount of research and development funds and launched their own software or hardware products and system application solutions.

1. Introduction

Radio Frequency Identification (RFID), also known as electronic tag (E-Tag), is a technology that uses radio frequency signals to automatically identify target objects and obtain relevant information. The earliest application of RFID can be traced back to the "friend or foe identification" system used to distinguish between Allied and Nazi aircraft in World War II. With the advancement of technology, the application field of RFID is expanding, and it now involves all aspects of people's daily life, and will become a basic technology for the construction of the future information society. Typical applications of RFID include: warehouse management, production line automation, and daily necessities sales in the logistics field; container and package management, highway toll collection and parking fees in the transportation field; management of sheep, fish, fruits, etc. in agriculture, animal husbandry and fishery, as well as tracking of pets and wild animals; in the medical industry, it is used for drug production, patient care, and medical waste tracking; in the manufacturing industry, it is used for visual management of parts and inventory; RFID can also be applied to a variety of application fields such as book and document management, access control management, positioning and object tracking, environmental perception, and check anti-counterfeiting.

At present, RFID has become a research hotspot in the IT industry and is regarded as the next "gold mine" of the IT industry. Major software and hardware manufacturers, including IBM, Motorola, Philips, TI, Microsoft, Oracle, Sun, BEA, SAP, etc., have shown great interest in RFID technology and its applications, and have invested a lot of research and development funds to launch their own software or hardware products and system application solutions. In the application field, a large number of companies represented by Wal-Mart, UPS, Gillette, etc. have begun to prepare to use RFID technology to transform their business systems in order to improve the work efficiency of the company and provide customers with various value-added services. In the field of labels, RFID tags have many advantages over barcodes, such as fast reading speed, large storage space, long working distance, strong penetration, diverse appearance, strong adaptability to the working environment, and reusability.

Therefore, it is undoubtedly very important to analyze the current status of RFID technology and look forward to its future.

2. Research status

Current RFID research mainly focuses on RFID technical standards, RFID tag costs, RFID technology, and RFID application systems.

2.1 RFID Technology Standards

The standardization of RFID is an important issue that needs to be solved urgently. Countries and relevant international organizations are actively promoting the formulation of RFID technical standards. At present, there is no complete international and domestic standard for RFID. The standardization of RFID involves multiple parts such as identification coding specifications, operation protocols and application system interface specifications. Among them, the identification coding specifications include identification length, encoding method, etc.; the operation protocol includes air interface, command set, operation process and other specifications. The current main RFID-related specifications are the EPC specifications of Europe and the United States, the UID (Ubiquitous ID) specifications of Japan and the ISO 18000 series of standards. Among them, the ISO standard mainly defines the air interface for interoperability between tags and readers.

The EPC specification is formulated by the Auto-ID Center and the later established EPCglobal. The Auto-ID Center was initiated and established by the Massachusetts Institute of Technology (MIT) in 1999. Its goal is to create a global "Internet of Things". The center has received extensive support from the US government and the business community. On October 26, 2003, the new EPCglobal organization was established to take over the work of the previous Auto-ID Center to manage and develop the EPC specification. Regarding tags, the EPC specification has issued the first generation of specifications.

The UID (Ubiquitous ID) specification is formulated by the Ubiquitous ID Center of Japan. The Ubiquitous ID Center of Japan was initiated and established by the T-Engine Forum. Its goal is to establish and promote automatic object identification technology and ultimately build a ubiquitous computing environment. The specification has no mandatory requirements for frequency bands. Both tags and readers are multi-band devices that can support 13.56MHz or 2.45GHz frequency bands at the same time. UID tags refer to all devices containing ucode codes, such as barcodes, RFID tags, smart cards, and active chips, and define 9 different categories of tags.

2.2 RFID Technology Research

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Currently, RFID technology research mainly focuses on operating frequency selection, antenna design, anti-collision technology, and security and privacy protection.

2.2.1 Operating frequency selection

The selection of operating frequency is a key issue in RFID technology. The selection of operating frequency must not only meet the needs of various applications, but also take into account the regulations of various countries on the use of radio frequency bands and transmission power. The current RFID operating frequency spans multiple frequency bands, and different frequency bands have their own advantages and disadvantages. It affects not only the performance and size of the tag, but also the price of the tag and the reader. In addition, the difference in radio transmission power affects the working distance of the reader.

The energy of low-frequency band is relatively low, the data transmission rate is low, and the wireless coverage range is limited. In order to expand the wireless coverage range, the size of the tag antenna must be enlarged. Although the low-frequency wireless coverage range is smaller than that of high-frequency wireless coverage range, the antenna is not very directional and has a relatively strong ability to bypass obstacles. The low-frequency band can use 1 to 2 antennas to achieve full coverage of the wireless range. In addition, the cost of low-frequency band electronic tags is relatively low, and they have a variety of shapes such as card-shaped, ring-shaped, and button-shaped. The energy of high-frequency band is relatively high and suitable for long-distance applications. The power loss of low frequency is proportional to the cube of the propagation distance, while the power loss of high frequency is proportional to the square of the propagation distance. Since high frequency propagates in the form of beams, it can be used for smart tag positioning. Its disadvantage is that it is easily blocked by obstacles, easily affected by factors such as reflection and human disturbance, and it is not easy to achieve full coverage of the wireless range. The data transmission rate of high-frequency band is relatively high, and the communication quality is better. Table 1 is a table of RFID frequency band characteristics.

2.2.2 RFID Antenna Research

An antenna is a device that receives or radiates the radio frequency signal power of a radio transceiver in the form of electromagnetic waves. Antennas can be divided into shortwave antennas, ultrashortwave antennas, microwave antennas, etc. according to the working frequency band; they can be divided into omnidirectional antennas, directional antennas, etc. according to the directionality; and they can be divided into linear antennas, planar antennas, etc. according to the shape.

Due to the limitations of application scenarios, RFID tags usually need to be attached to the surfaces of objects of different types and shapes, or even embedded inside objects. RFID tags require low cost and high reliability. In addition, the tag antenna and reader antenna also bear the role of receiving energy and transmitting energy respectively. These factors put forward strict requirements on the design of antennas. Current research on RFID antennas mainly focuses on studying the impact of antenna structure and environmental factors on antenna performance.

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The antenna structure determines the antenna pattern, polarization direction, impedance characteristics, standing wave ratio, antenna gain and working frequency band. Directional antennas are more suitable for electronic tag applications because they have less return loss; since the placement direction of RFID tags is uncontrollable, the reader antenna must adopt circular polarization (its antenna gain is larger); the antenna gain and impedance characteristics will have a greater impact on the range of the RFID system; the antenna's working frequency band has a greater impact on the antenna size and radiation loss.
Antenna characteristics are affected by the shape and physical properties of the identified object. For example, metal objects have an attenuation effect on electromagnetic signals, metal surfaces have a reflective effect on signals, elastic substrates can cause deformation of tags and antennas, and the size of objects has certain restrictions on the size of antennas. People have proposed a variety of solutions based on the above characteristics of antennas, such as using zigzag antennas to solve size limitations and inverted F-type antennas to solve reflection problems on metal surfaces.

Antenna characteristics are also affected by the objects and environment around the antenna. Obstacles will hinder the transmission of electromagnetic waves; metal objects will produce electromagnetic shielding, which will make it impossible to correctly read the content of the electronic tag; other broadband signal sources, such as engines, water pumps, generators, and AC/DC converters, will also produce electromagnetic interference, affecting the correct reading of electronic tags. How to reduce electromagnetic shielding and electromagnetic interference is an important direction of RFID technology research.

2.2.3 Anti-collision technology research

Given that multiple electronic tags work at the same frequency, when they are within the range of the same reader, if no multiple access control mechanism is adopted, the information transmission process will generate conflicts, resulting in information reading failure. At the same time, the overlapping working ranges between multiple readers will also cause conflicts. The Colorwave algorithm is proposed in the literature to solve the reader conflict problem. According to the different working frequency bands of electronic tags, different anti-collision algorithms are proposed. For tag conflicts, in the high frequency (HF) band, the anti-collision algorithm of the tag generally adopts the classic ALOHA protocol. Tags using the ALOHA protocol avoid conflicts by selecting a method to transmit information to the reader after a random time. Most high-frequency readers can scan dozens of electronic tags at the same time. In the ultra-high frequency (UHF) band, the tree bifurcation algorithm is mainly used to avoid conflicts. Compared with high-frequency band electronic tags using the ALOHA protocol, the tree bifurcation algorithm leaks more information and has poor security.

The above two tag anti-collision methods are both time division multiple access (TDMA) methods, which are widely used. In addition, some people have proposed anti-collision algorithms for frequency division multiple access (FDMA) and code division multiple access (CDMA), which are mainly used in broadband application scenarios such as ultra-high frequency and microwave.

2.2.4 Security and Privacy Issues

RFID security issues focus on the privacy protection of individual users, the protection of business secrets of corporate users, the prevention of attacks on RFID systems, and the use of RFID technology for security prevention. The challenges are:

(1) Ensure that the user's tag information is not accessed without authorization, so as to protect the user's privacy in terms of consumption habits, personal whereabouts, etc.;

(2) Avoid being used to steal users’ business secrets because the RFID system has a fast reading speed and can quickly scan all products in the supermarket and track changes;

(3) Protection against various attacks on RFID systems, such as: rewriting tags to tamper with item information; using special equipment to forge tag responses to deceive readers and writers to create the illusion that items exist; eavesdropping on tag information from a distance based on the asymmetry of the RFID forward and backward channels; implementing denial of service attacks by interfering with the RFID operating frequency; destroying tags by emitting specific electromagnetic waves, etc.

(4) How to use the unique identification feature of RFID for access control security, check anti-counterfeiting, product anti-counterfeiting, etc.

2.3 RFID Application Research

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The unique identification feature of RFID tags for objects has triggered a wave of research on applications based on RFID technology. Logistics and the Internet of Things are the current hot spots in RFID application research, and other application research also includes spatial positioning and tracking, ubiquitous computing, system security and many other aspects.

2.3.1 Logistics and the Internet of Things

The physical Internet is to build an information network of all items involved in circulation on the basis of the existing Internet by attaching RFID tags to all items. The establishment of the physical Internet will have a profound impact on all aspects of the circulation of items, such as production, sales, transportation, use, and recycling, and will have a profound impact on the behavior of governments, enterprises, and individuals. Through the physical Internet, any item in the world can be identified, tracked, and monitored on demand anytime, anywhere. The physical Internet is regarded as another revolution in the IT industry after the Internet.

2.3.2 Spatial Positioning and Tracking

The popularity of wireless and mobile communication devices has led to people's demand for location-aware services. People need to determine the three-dimensional coordinates of objects and track their changes. Existing positioning service systems mainly include GPS systems based on satellite positioning, infrared or ultrasonic positioning systems, and mobile network-based positioning systems. The popularity of RFID provides a new solution for spatial positioning and tracking services for people and objects. The RFID positioning and tracking system mainly uses the unique identification characteristics of tags for objects, and measures the spatial position of objects based on the signal strength of radio frequency communication between the reader and the tag installed on the object. It is mainly used for indoor positioning where GPS systems are difficult to apply.

2.3.3 Ubiquitous Computing

RFID tags have the ability to uniquely identify objects. By combining with sensor technology, they can sense the temperature, humidity, light and other status information of surrounding objects and the environment, and use wireless communication technology to conveniently transmit this status information and its changes to the computing unit, thereby improving the visibility of the environment to the computing module and building the infrastructure for future ubiquitous computing, making computing ubiquitous and providing services to people proactively and on demand.

3 Conclusion

RFID will build a bridge between the virtual world and the physical world. It is foreseeable that in the near future, RFID technology will not only be widely adopted in all walks of life, but will eventually be integrated with ubiquitous computing technology, which will have a profound impact on human society.

As a global manufacturing base, China will be the world's largest RFID application market in the future. This will be a rare opportunity for domestic scientific research institutions and enterprises. At present, my country's research on core technologies such as RFID chips and RFID system security is almost blank, and RFID applications are still in the initial stage. However, it is believed that under the environment of government promotion and corporate participation, and attracted by the huge market space, more and more companies and research institutions in China will participate in the research and development and application of RFID technology, and more companies will use RFID technology to carry out enterprise information transformation. China will not only dominate the application market of RFID technology, but also become the global research and development center of RFID technology.